宽带相干反斯托克斯喇曼散射法诊断固体燃剂燃烧场

 报道了采用单次脉冲非稳腔空间增强探测 相干反斯托克斯喇曼散射（USED CARS）技术诊断常压下固体燃剂瞬态燃烧场温度和氮气浓度。采用宽带USED CARS技术，在固体燃剂瞬态燃烧场获得了较高信噪比的单次激光脉冲氮气Q支CARS实验谱，用CARS理论计算软件拟合CARS实验谱，给出了固体燃剂瞬态燃烧场温度和氮气浓度在不同高度的分布，固体燃剂燃烧场温度约2 250K、氮气相对浓度16%～20%。     

宽带相干反斯托克斯喇曼散射法诊断固体燃剂燃烧场

报道了采用单次脉冲非稳腔空间增强探测 相干反斯托克斯喇曼散射（USED CARS）技术诊断常压下固体燃剂瞬态燃烧场温度和氮气浓度。采用宽带USED CARS技术,在固体燃剂瞬态燃烧场获得了较高信噪比的单次激光脉冲氮气Q支CARS实验谱,用CARS理论计算软件拟合CARS实验谱,给出了固体燃剂瞬态燃烧场温度和氮气浓度在不同高度的分布,固体燃剂燃烧场温度约2 250K、氮气相对浓度16%～20%。     

The three-dimensional numerical simulation of aluminized composite solid propellant combustion

A three-dimensional numerical framework is presented that examines the burning of aluminized solid propellants. The numerical solver accounts for heat conduction in the solid, combustion in the gas phase, and coupling of these by means of a level set method. The aluminium particles are treated as heat conducting solid spheres. The aluminium particle detachment process is modelled using level sets, but once the particle becomes free from the surface, its subsequent motion in the gas phase is governed by particle dynamics. Some preliminary calculations of the three-dimensional combustion field supported by a pack with embedded aluminium particles are presented.     

The application of CARS for temperature measurements in high pressure combustion systems

The determination of accurate temperatures from CARS N₂ Q-branch spectra in premixed flames is discussed for pressures up to 40 bar. The influence of collisional line narrowing in the CARS spectra is modelled by a MEG fitting law. It takes into account collisions of N₂ with CO₂ and H₂O. The analysis of the CARS data showed that the non-resonant background has an increasing influence on temperature with increasing pressure. Little influence on the quality of the fit between theory and experiment was found. Since there is a danger of residual systematic temperature deviations, which cannot be identified from the quality of the fit, spontaneous rotational Raman scattering is employed as an independent measuring technique.     

CARS in combustion: Prospects and problems

The principles of CARS are reviewed. This technique has achieved important successes in combustion, but its use has been limited mostly to temperature measurements. We demonstrate the feasibility of sensitive single-shot concentration measurements (to 0.2%) with fair accuracy, in spite of the adverse effects of turbulence and saturation. Even better sensitivities will be achieved using electronic resonance enhancement.     

固体推进剂燃烧驱动CO2气动激光小信号增益测量

介绍了固体推进剂燃烧驱动CO2气动激光小信号增益测量的原理、方法及实验系统,重点说明小信号增益测量光路设计、热敏电阻红外探测器工作原理、增益输出信号滤波和放大电路设计及数据采集系统的硬件配置和软件编制原则,给出典型实验测量结果。实验证明,采用放大法可较为准确的测量固体推进剂燃烧驱动CO2气动激光小信号增益。     

固体推进剂燃烧驱动CO_2气动激光小信号增益测量

介绍了固体推进剂燃烧驱动 CO2 气动激光小信号增益测量的原理、方法及实验系统 ,重点说明小信号增益测量光路设计、热敏电阻红外探测器工作原理、增益输出信号滤波和放大电路设计及数据采集系统的硬件配置和软件编制原则 ,给出典型实验测量结果。实验证明 ,采用放大法可较为准确的测量固体推进剂燃烧驱动 CO2 气动激光小信号增益     

A study of CARS nitrogen thermometry at high pressure

The accuracy of CARS N₂ thermometry has been assessed using carefully measured experimental data at high pressures for the temperature range 295 to 870 K and pressure range 1–20 bar. Excellent agreement between calculated and experimental spectra was achieved using statistically based fitting laws to model rotational relaxation. Temperature errors of within ±60 K were achieved using the MEG fitting law, and within ±30 K using an extension to the model (XMEG). Results of separate ab initio IOS calculations with ECS corrections for rotational relaxation gave good overall agreement but did not model the structure of the motionally narrowed spectra as well as the empirical models. The various models were also compared with some complementary data measured by DLR, Stuttgart in their high pressure burner for pressures up to 40 bar. This study also investigated the sensitivity of CARS thermometry to pressure; in certain regions a significant reduction in sensitivity was found. Other key factors investigated include nonlinearities in the intensified diode array detector.Work supported by the CEC Project Turbulent Combustion and Diagnostics and by AEA Technology Underlying Programme     

Flame structure of HMX/GAP propellant at high pressure

The chemical and thermal structure of a HMX/GAP propellant flame was investigated at a pressure of 0.5 MPa using molecular beam mass spectrometry and a microthermocouple technique. The pressure dependence of the burning rate was measured in the pressure range of 0.5–2 MPa. The mass spectrometric probing technique developed for flames of energetic materials was updated to study the chemical structure of HMX/GAP flames at high pressures. Eleven species, including HMX vapor, were identified, and their concentrations were measured in a zone adjacent to the burning surface at pressures of 0.5 and 1 MPa. Temperature profiles in the propellant combustion wave were measured at pressures of 0.5 and 1 MPa. Species concentration profiles were measured at 0.5 MPa. Two main zones of chemical reactions in the flame were found. The data obtained can be used to develop and validate combustion models for HMX/GAP propellants.     

Binder melt: Quantification using SEM/EDS and its effects on composite solid propellant combustion

The present study reports the development of a novel technique to quantify binder melt on the surface of the propellant. Non-aluminized AP-HTPB propellants of 86% particulate loading are used to illustrate the technique. Elemental maps of unburnt and extinguished propellant surface are obtained using EDS (Energy Dispersive Spectroscopy). Overlap between the elements is identified and the elemental maps are processed to calculate AP and binder area exposed in unburnt and extinguished samples. The AP area exposed is found to be around 72.3% and 63.3% for unburnt and extinguished samples, respectively, indicating a reduction in AP exposed area with extinguished samples. This has been attributed to the binder melt discussed in literature but never quantified. Simulations have been carried out to analyze and understand the effects of this binder melt. A random packing algorithm is used to simulate propellant packs. Also, a methodology to account for binder melt layer is introduced and is used to capture AP exposed areas. Effect of binder melt in propellants with different solid loading and varying particle size is discussed. It is shown that fine AP particles are more prone to being covered by binder melt than the coarse AP particles. A possible explanation to the behavior of plateau burning propellants observed in literature has been provided through this analysis.     

固体推进剂燃烧驱动CO2气动激光小信号增益测量

 介绍了固体推进剂燃烧驱动CO₂气动激光小信号增益测量的原理、方法及实验系统,重点说明小信号增益测量光路设计、热敏电阻红外探测器工作原理、增益输出信号滤波和放大电路设计及数据采集系统的硬件配置和软件编制原则,给出典型实验测量结果。实验证明,采用放大法可较为准确的测量固体推进剂燃烧驱动CO₂气动激光小信号增益。     

Travelling wave mathematical analysis and efficient numerical resolution for a one-dimensional model of solid propellant combustion

We investigate a model of solid propellant combustion involving surface pyrolysis coupled to finite activation energy gas-phase combustion. Existence and uniqueness of a travelling wave solution are established by extending dynamical system tools classically used for premixed flames, dealing with the additional difficulty arising from the surface regression and pyrolysis. An efficient shooting method allows to solve the problem in phase space without resorting to space discretisation nor fixed-point Newton iterations. The results are compared to solutions from a CFD code developed at ONERA, assessing the efficiency and potential of the method, and the impact of the modelling assumptions is evaluated through parametric studies.     

Multiplex CARS measurements in supersonic H2/air combustion

2 and O₂ multiplex coherent anti-stokes Raman spectroscopy (CARS) employing a single dye laser has been explored to simultaneously determine the temperature and concentrations of H₂ and O₂ in a hydrogen-fueled supersonic combustor. Systematic calibrations were performed through a well-characterized H₂/air premixed flat-flame burner. In particular, temperature measurement was accomplished using the intensity ratio of the H₂ S(5) and S(6) rotational lines, whereas extraction of the H₂ and O₂ concentrations was obtained from the H₂ S(6) and O₂ Q-branch, respectively. Details of the calibration procedure and data reduction are discussed. Quantification of the supersonic mixing and combustion characteristics applying the present technique has been demonstrated to be feasible. The associated detection limits as well as possible improvements are also identified. Received: 1 July 1997/Revised version: 29 September 1998     

1维非稳腔空间增强探测CARS技术对稳态燃烧场温度的测量

 建立了1维非稳腔空间增强探测CARS实验系统，该系统由光源（YAG激光器、染料激光器）、实验光路和信号采集系统组成。分别测量了空气和化学平衡比为1，甲烷流量为0.7 L/min的甲烷-空气预混火焰中的氮气Q支的CARS实验谱。给出了火焰不同高度处小范围内的温度分布结果，并对实验结果进行了分析，结果表明：预混火焰温度随高度的增加呈下降趋势，测量结果的不确定度优于7%。该技术可用于稳态燃烧场温度的测量。     

CARS study of deuterium clusters stabilized in solid helium

Solid deuterium clusters that for the first time have been isolated in a matrix of solid helium have been investigated at T=1.3 K and P=3 MPa by the coherent anti-Stokes Raman spectroscopy (CARS) technique. The vibronic Q₁((J=0) and Q₁(J=1) line intensity, shape, and positions have been studied as functions of ortho and para content in the solid, as well as of the size of clusters. The strong effect of Raman scattering cross-section sensitivity to the molecular environment nuclear spin state has been found in CARS: the ratio of probabilities for the scattering by para(J=1) and ortho(J=0) deuterium, which is equal to 1 in a gas, is as high as 10000 in nearly pure ortho deuterium, whereas it is about 50 in spontaneous Raman scattering. This effect has been shown to occur starting from a cluster size corresponding to the onset of the phonon band.     

1.315 μm波长附近实际大气高分辨率吸收光谱

用窄线宽、脉冲可调谐光参量振荡器（OPO）作光源,使用光程长达1 097m的怀特池,采用单探测器分时复用的探测方法,首次在吸收池中精确测量了实际大气中1.315 μm波长附近高分辨率吸收光谱,实验验证了实际大气中水汽是该波段的主要吸收气体;得到了实际大气中吸收分子在氧碘激光波长（7 603.14cm-11）处的吸收截面为 (1.05±0.09)×10-24 cm2(标准大气条件下）以及在该波段主要吸收谱线的参数,包括吸收线的位置、线强度、压力加宽半宽度等。利用实测的线参数计算了在氧碘激光波长附近大气分子的吸收截面,发现吸收最小的波长分别位于7 603.31和7 603.93cm-1,其值约为(8.9±0.8)×10-25 cm2,比氧碘激光波长处的吸收截面约小15%。     

Unsteady regimes of propellant combustion in a semiclosed space

Numerical simulations were used to study the nonstationary modes of propellant combustion in a semiclosed volume outside the boundaries of stationary combustion. The analysis was performed within the framework of phenomenological theory of nonstationary combustion for the simplest propellant combustion model containing the minimum number of governing parameters. It was demonstrated that the variation of one of the parameters can bring about the changeover from the stationary regime to the chaotic one according to the Feigenbaum scenario. A still further increase in the bifurcation parameter initiates transition to experimentally observed combustion regimes (extinction and so-called sneezing).     

1.315 μm波长附近实际大气高分辨率吸收光谱

 用窄线宽、脉冲可调谐光参量振荡器（OPO）作光源，使用光程长达1 097m的怀特池，采用单探测器分时复用的探测方法，首次在吸收池中精确测量了实际大气中1.315 μm波长附近高分辨率吸收光谱，实验验证了实际大气中水汽是该波段的主要吸收气体；得到了实际大气中吸收分子在氧碘激光波长（7 603.14cm^-11）处的吸收截面为 (1.05±0.09)×10^-24 cm²(标准大气条件下）以及在该波段主要吸收谱线的参数，包括吸收线的位置、线强度、压力加宽半宽度等。利用实测的线参数计算了在氧碘激光波长附近大气分子的吸收截面，发现吸收最小的波长分别位于7 603.31和7 603.93cm^-1，其值约为(8.9±0.8)×10^-25 cm²，比氧碘激光波长处的吸收截面约小15%。